Sheet metal waveguide constructed of a pair of interlocking sheet metal channels

ABSTRACT

A sheet metal waveguide includes a pair of sheet metal channels with each channel having a double bend or fold along each of two substantially parallel leg sections. The channels are arranged relative to each other such that a portion of a leg suction of one channel overlaps a portion of a leg section of the other channel in a manner to form a waveguide having recesses on opposite broad walls thereof suitable for receiving and holding a dielectric body therebetween. The ends of the leg sections of one channel are clipped and thereby held within a bend or fold in the leg sections of the other channel.

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A sheet metal waveguide includes a pair of sheet [73] Asslgnee C Corporatmn metal channels witheach channel having a double [22] Filed:

bend or fold along each of two substantially parallel leg sections. The channels are arranged relative to June 24, 1971 [21] 156397 each other such that a portion of a leg suction of one channel overlaps a portion of a leg section of the other channel in a manner to form a waveguide having recesses on opposite broad walls thereof suitable for receiving and holding a dielectric body therebetween.

, The ends of the leg sections of one channel are clipped and thereby held within a bend or fold in the leg sections of the other channel.

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[56] References Cited UNITED STATES PATENTS 4 Claims, 1 Drawing Figure 2,381,367 Quayle... ..........333/95 R x Patented Aug. '22, 1972 3,686,590

' INVENTOR. illiam A. Hiselwri ATTORNEY The invention herein described was made in the course of a contract or subcontract with the Department of the Navy.

This invention relates to waveguides and more particularly to those waveguide structures which include therein a dielectric body. When the dielectric body is of ferrite or garnet material, for example, this waveguide structure may provide the functions of phase shifting, isolation and limiting alongthe waveguide section.

Such waveguide structures are conventionally made by extruding tubing to the required dimension. A. dielectric body, such as garnet, is dimensioned so as to properly fit within the waveguide. The dielectric body is fixed to the waveguide by bonding the dielectric material in the waveguide in a proper aligned fashion with low stresses on the body. The procedure is costly since the dielectric body in the waveguide must meet rather close tolerances to minimize gaps and stresses between the dielectric body and the waveguide.

Further, if the coefficient of expansion or contraction of the waveguide material and the dielectric material differ substantially, the bond or the dielectric body itself may break with changes in temperature. When the dielectric material is garnet and isused to make a phase shifter, this material is biased by a proper d.c. magnetic field. Stresses due to magnetostriction associated with this field may be developed in the material due to the fixedly held material in the extruded tubing. These stresses in the material produce improper phase shift. Also, the assembly of the body inside the waveguide for proper fit, contact pressure and straightness is made more difficult due to the limitedaccess inside the enclosed waveguide structure.

In accordance with the present invention, the above disadvantages are avoided by a dielectrically loaded waveguide having a pair of sheet metal channel members and a dielectric body. Each sheet metal channel member has a pair of substantially parallel leg sections. Each leg section has a double bend such that a portion of the leg section is twice bent on itself, forming a recessed portion on the inner surface of the leg section. The channel members are assembled with the dielectric body such that the recessed portions of the leg sections of one channel member overlap the recessed portions of the leg sections of the other channel member to form recessed opposite waveguide walls with the dielectric body closely fitted between the recesses. The leg sections of one channel member interlock with the leg sections of the other by clipping ends of one'channel members leg sections in the bends of the other channel members leg sections.

Further description follows in conjunction with the single illustration which is a perspective view of a dielectrically loaded waveguide in accordance with the present invention.

Referring to the illustration, there is shown a waveguide constructed of a pair of sheet metal channel members 1 l and 13 and a rectangularly shaped garnet toroid 14. The channel members may be, for example, of aluminum sheet metal bent in the form of a substantially U-shaped or channel configuration. The channel member 11 includes a pair of substantially parallel leg sections 15 and 17 spaced by a center sec- I tion 19. The leg sections 15 and 17 each have astep 18 and 20 on the inner surface of the leg sections forming recessed portions 27 and 28 on the inner surface of the channel member 11. The steps 18 and 20 are each formed by the leg section being bent so as to fold twice on itselfas shown in the Figure Likewise, channel member 13 includes a pair of leg sections 21 and 23 spaced by a center section 25. The leg sections 21 and 23 are arranged as sections 15 and 17 of channel member 11 to form steps 22 and 24 on the inner surface of the respective leg sections 21 and 23. The leg sections 21 and 23 are each twice bent on itself as shown in the Figure to form the steps 22 and 24 and recessed portions 29 and 31 on the inner surface of the channel member 13. The double bend of each leg section 15, 17, 21 and 23 is arranged such that the inside fold of the second bend always faces away from the center section of the associated channel member.

Channel members 11 and 13 are arranged such that the recessed portions 27 and 28 of leg sections 15 and 17 overlap the recessed portions 29 and 31 of leg sections 21 and 23, respectively, to form a section of waveguide with a recess on each of the opposite broad walls of the waveguide. The depth of the step, the amount'of overlap of the leg sections and the location of the step are selected so that a toroid 14 of garnet material closely fits within the recesses of the broad walls so formed. The toroid 14 is securely held to the waveguide so formed by the spring-like contact pro-. vided by the first bend 33, 35, 37 and 39 of the respective leg sections 15, 17, 21 and 23.

The channel member 11 is interlocked with the channel member 13 by fitting the end 40 of leg section 21 into the second bend 41 of the leg section 15 and by fitting the end 42 of the leg section 23 into the second bend 43 of leg section 17. The second bends 41 and 43 of leg sections 15 and 17 act to clip or hold the ends of leg sections 21 and 23 respectively. The spacing between the recessed portions 29 and 31 and 27 and 28 may be slightly undersized relative to the size of the toroid 14 to provide a controlled contact pressure on the toroid 14 by the spring action associated with the double bends of the leg sections 15, 17, 23 and 21.

' Suitable bonding material may be provided between overlapping recessed portions 27, 29 and 28, 31 once the channel members are assembled together. The

bends must be sharp enough to allow a tight fit or connection with the clipped ends to provide good electrical contact between channel members 11 and 13.

An aperture 47 of the toroid 14 may be filled by an insulated biasing wire 45 embedded in a body 48 of suitable dielectric material. The dielectricconstant of the toroid 14 and of the dielectric body 48 may be on the order of, for example, 15. In operation, the biasing wire is coupled to a suitable source of d.c. potential,

other channel member to a depth that will match the width of the toroid. The recess is thereby formed to the width of the toroid without the need of closely toleranced dimensions. The nature of the bends in the channel members makes the broad walls somewhat flexible to allow for differences in thermal expansion between the toroid and the waveguide and yet hold the toroid. The nature of the bends also allows the recessed waveguide broad walls to lie flush across the flat sided toroid ends. Also, the toroid is held securely to the waveguide and yet allows the lateral extension or contraction of the toroid with magnetostrictive stresses.

I claim:

1. A waveguide comprising:

a pair of sheet metal channel members each having a pair of substantially parallel leg sections spaced by a substantially perpendicular center section, each of said leg sections having a recessed inner surface portion formed by a portion of each leg section being bent so as to fold twice on itself,

a dielectric body,

said channel members being arranged such that said recessed inner surface portions overlap each other to form a section of waveguide having recesses on each of the opposite broad walls of the waveguide adapted to receive said body with said channel members being interlocked to each other by the ends of the leg sections of one channel member being fitted individually into the respective folds in the leg sections of the other channel member.

2. A waveguide as claimed in claim 1 wherein said body is a toroid of magnetic material, a wire running through the center of said toroid to which a direct current potential can be applied for establishing a desired magnetic field in said toroid.

3. A waveguide comprising:

first and second sheet metal channel members each having a pair of substantially parallel leg sections separated by a center section,

each leg section including a stepped portion formed by first bending the leg section at a point along its length back towards the center section and then bending the leg section at said point back to the original direction of said leg section thereby forming a double bend, the inside fold of the second bend so formed facing away from said center sectron,

said channel members being interlocked by overlapping the stepped portions of the leg sections with the ends of the leg sections of one channel member being fitted individually into the respective second bends in the leg sections of the other channel member.

4. The method of making a waveguide including a dielectric body comprising the steps of:

forming a pair of channel shaped members each having a pair of substantially parallel leg sections and an intermediate orthogonal center section,

bending a portion of each leg section such that each leg section is twice bent on itself in a manner to form a recess along a portion of each leg section and so that the inner surface of the second bend faces away from said center section,

overlapping the recessed portions of the leg sections 3%a:lzgttzrlorsamtarshsss ifiifilt form a section of waveguide with recesses on each of opposite walls of the waveguide adapted to receive opposite ends of said body, and

interlocking said channel members by fitting the ends of the leg sections of one channel member individually into the respective second bends in the leg sections of the other channel member. 

1. A waveguide comprising: a pair of sheet metal channel members each having a pair of substantially parallel leg sections spaced by a substantially perpendicular center section, each of said leg sections having a recessed inner surface portion formed by a portion of each leg section being bent so as to fold twice on itself, a dielectric body, said channel members being arranged such that said recessed inner surface portions overlap each other to form a section of waveguide having recesses on each of the opposite broad walls of the waveguide adapted to receive said body with said channel members being interlocked to each other by the ends of the leg sections of one channel member being fitted individually into the respective folds in the leg sections of the other channel member.
 2. A waveguide as claimed in claim 1 wherein said body is a toroid of magnetic material, a wire running through the center of said toroid to which a direct current potential can be applied for establishing a desired magnetic field in said toroid.
 3. A waveguide comprising: first and second sheet metal channel members each having a pair of substantially parallel leg sections separated by a center section, each leg section including a stepped portion formed by first bending the leg section at a point along its length back towards the center section and then bending the leg section at said point back to the original direction of said leg section thereby forming a double bend, the inside fold of the second bend so formed facing away from said center section, said channel members being interlocked by overlapping the stepped portions of the leg sections with the ends of the leg sections of one channel member being fitted individually into the respective second bends in the leg sections of the other channel member.
 4. The method of making a waveguide including a dielectric body comprising the steps of: forming a pair of channel shaped members each having a pair of substantially parallel leg sections and an intermediate orthogonal center section, bending a portion of each leg section such that each leg section is twice bent on itself in a manner to form a recess along a portion of each leg section and so that the inner surface of the second bend faces away from said center section, overlapping the recessed portions of the leg sections of one channel member with the recessed portions of the leg sections of the other channel member to form a section of waveguide with recesses on each of opposite walls of the waveguide adapted to receive opposite ends of said body, and interlocking said channel members by fitting the ends of the leg sections of one channel member individually into the respective second bends in the leg sections of the other channel member. 